1. Technical Field
The present invention relates to a display device including a microcapsule and a method for manufacturing the same, and an electronic apparatus equipped with the display device.
2. Related Art
In the related art, an electrophoretic display device which has an electrophoretic dispersion liquid including a liquid dispersion medium and electrophoretic particles is known. When an electric field is applied to the electrophoretic dispersion liquid, a distribution of the electrophoretic particles is changed and an optical characteristic of the electrophoretic dispersion liquid changes. The electrophoretic display device utilizes this optical characteristic change to display. Since such electrophoretic display device does not require a backlight, it can contribute to reducing the cost and making the display device thinner. Further, because the electrophoretic display device has a memory effect of the display in addition to a wide viewing angle and a high contrast, it attracts a lot of attention as a next-generation display device.
An electrophoretic display device in which the electrophoretic dispersion liquid is encapsulated in a microcapsule is also proposed as described in a first example of related art, for example. Encapsulating the electrophoretic dispersion liquid into the microcapsule has an advantage in that the spill of the dispersion liquid during the manufacturing process of the display device can be prevented and precipitation and aggregation of the electrophoretic particles can be reduced.
In a case where an electrophoretic display device equipped with such microcapsule is manufactured, generally, the microcapsule is coated on a whole surface of a substrate on which a common electrode is formed. Then, a substrate on which a pixel electrode is formed is bonded on the coated surface of the microcapsule so as to be laminated (e.g. refer to a second, third, and fourth examples of related art).
A method is also known in which the microcapsule is discharged from the inkjet nozzle on the pixel electrode one by one using the inkjet method (e.g. refer to a fifth example of related art).
The examples of related art are as follows: Japanese Unexamined Patent No. 1-86116 is the first example; Japanese Unexamined Patent No. 2002-318396 is the second example, particularly paragraph [0004]; Japanese Unexamined Patent No. 2002-532756 is the third example, particularly FIG. 7B; SID 98 DIGEST pp. 1014-1017 is the fourth example; and Japanese Unexamined Patent No. 2000-35769 is the fifth example.
However, the method in which the microcapsule is coated on the whole surface of the substrate on which the common electrode is formed has the following disadvantages.
(1) A material is partially wasted. Because, the microcapsule is coated on the whole surface of the substrate, so that the microcapsule is also coated on an area other than a display area forming an actual display and a background area forming the background of the display area.
(2) The background is simply purposed to allow the display of the display area to be clearly observed, and originally, not required to change its display. Therefore, driving the background so as to be a background color results in waste in a circuit configuration. Additionally, coating the microcapsule on the background causes waste of the material.
(3) In a case where the display device is made by bonding each substrate, typically, a conductive part is formed on one substrate. The conductive part applies a voltage to the other substrate. Then, the substrates are bonded so that the conductive part is electrically conducted to the electrode of the other substrate. That is, in the aforementioned examples, typically, the conductive part is formed in advance on the substrate on which the pixel electrode is formed. The substrate on which the pixel electrode is formed and the substrate on which the common electrode is formed are bonded so that the conductive part is electrically conducted to the common electrode. However, the microcapsule is coated on the whole surface of the substrate on which the common electrode is formed. Thus, the microcapsule should be removed from a part that is electrically conducted to the conductive part before bonding. In order to remove the microcapsule, for example, a method that stripes it mechanically or chemically using solvents, etc., is employed. However, either method gives damages to the common electrode serving as a lower layer. As a result, display characteristics of the resulting display device are lowered. In addition, the removal of the microcapsule that has been coated results in the waste of the material.
(4) Typically, after bonding the substrates, the space between the peripheral parts of the substrates is sealed to protect the electrode and microcapsule from moisture, etc. If the microcapsule is coated to the sealed part, lowering sealing ability between the substrates. Accordingly, the microcapsule disposed at the peripheral part of the substrate is required to be removed before bonding them. However, the removal of the microcapsule causes the same disadvantage as that is described in (3).
The method in which the microcapsule is discharged from the inkjet nozzle on the pixel electrode one by one has a disadvantage in that it requires discharging a number of microcapsules for coating, lowering productivity due to the longer coating time.